Variable pitch propeller



Sept.'26, 1944. w. w. EvERTs 2,358,967

VARIABLE P ITCH PROPELLER Filed Oct. 6, 1942 2 Sheets-Sheet 1 p 26, 4- Iw. w. EVERTS VARIABLE PITCH PROPELLER 2 Sheets-Sheet 2 Filed Oct. 6,1942 Walter WEvez-ts a propeller of the the torque of tion produced bynection, in swinging the connecting means Patented se r. 26,1944

' UNITED STAT Walter w. Ever-ts, Baltimore,

Everel Propeller Corporation, corporation of Maryland ApplicationOctober c, 1942, Serhl Mil, asaimor to Baltimore, Hit, a

Claims. (CL 170-162) An important object of the invention is to providea propeller for aircraft or the like, the blades of which have theirpitch automatically varied by a pressure element. responsive to changesin pressure caused by the travel of the aircraft, while the torque ofthe motor remains substantially constant.

A further object above mentioned character so constructed that thevariable pitch blades will have the desired minimum pitchwhen thepropeller is rotating and the aircraft is not travelof the invention isto provide I ling, while the pitch of the blades will be automaticallyincreased when the aircraft is in flight,

R. P. M. of the motor autoconstant, but the adjustment/of thematically'slows down without throttle.-

A'further object of the invention is to provide centrifugally operatedmeans for maintaining the blades at the minimum desired pitch when thepropeller is rotating and while the aircraft is not the motor remainingsubstantially are employed to designate travelling, operating inconjunction with pressure operated means thrown into action during thetravel of the aircraft and overcoming the centrifugal action of thecentrifugally operated means, to automatically increase the pitch of thepropellers. a

A further object of the invention-is to provide 7 a pressure operatedelement arranged substantially in advance of the propeller and so shapedthat the air pressure acting upon its front face produces the maximumpressure thereon, while a suction is produced upon the rear face of thepressure element, in addition to the suction acthe centrifugalaction ofthe rotating blades.

A further object of the invention is to connect the pressure actuated.element with the blades in'a manner to increase the leverage of theconblades to vary their pitch. A further object of the invention is toprovide between the pressure actuatedelement and generally radialstabilizing arms which serve to vary the pitch of the blades, thestabilizing arms assuming inclined positions toincreasethe pitch of theblades and the connecting means moving outwardly toward the outer endsof the arms by virtue of their inclination, to increase the leverage.

A further object of the invention is to provide centrifugally operatedmeans for connecting permit of the pressure element and thestabilizingarms so that the centrlfugally operated means automati. callymoves toward the outer ends of the stabilizing arms to increase theleverage for turning the blades .when increasing their pitch.

A further object of the invention is to provide a universal mounting forthe pressure operated element so that this element in addition tonormally varying the pitch of the blades will also a differential pitchaction between the blades when the aircraft is turning in' a sharpcurve.

A further object of the invention is to mount separate pressure operatedelements upon the stabilizing arms. i

Other objects and advantages-of the invention will be apparent duringthe course of the following'description.

In the accompanying drawings forming a part in which like numerals likeparts throughout of this application and the same,

Figure 1 is a front elevation of a variable propeller embodying myinvention,

Figure 2 is an edge elevation of the same,

Figure 3 is a horizontal section taken on line 3-3 of Figure l,showingthe stabilizing arms in the radial position and the blades at thedesired minimum pitch,

Figure 4 is a similar view, showing the stabilizing arms shifted to therear inclined position and the blades at the maximum pitch,

Figure 5 is a detailed section of Figure 2,

Figure 6 is an exploded perspective view of the propeller, and,

Figure '7 is a perspective view of a propeller embodying a modified formof the invention.

In the drawings, wherein illustration is shown preferred embodiments ofmy invention, attention being called first to Figures 1 to 6, inclusive,the hub of the propeller, comprising a sleeve H which is suitablyrigidly mounted upon the drive shaft of the engine of aircraft or othervehicles. The sleeve has collars l2, preferably formed integraltherewith, and these collars are connected at their front by a web i3,also preferably formed'integral therewith. The collars I! arecylindrical and their axes are radial with respect to the sleeve II. Theweb l3 has'a shaft l4 projecting forwardly beyond same and rigidlysecured thereto and the longitudinal this shaft is in alinement with thelongitudinal axis of the sleeve ll.

pitch taken on line 5-5 for the purpose of the numeral i0 designatesaxis of.

placement by said screws 29 or the like.

. is placed upon the coupling 35.

Th collars l2, see Figure. 5, are provided at their inner endswithinwardly projecting flanges l5, and these collars are internally screwthreaded, as shown at l6. Arranged within each collar I2 is anend-thrust bearing l1, held in position by a ring-nut l8, having a screwthreaded portion engaging the screw threads I6. Extending through thecenter of .the hearing If! is a coupling-rod l9, provided at its innerend witha head 20. The. coupling rod is provided with screw threads 26upon its outer portion, and

' this outer screw threaded portion has screw threaded engagement withina radial coupling of means of rotation of the element or disc 3|.

- The connecting arms 40 are resilient and are acted upon by centrifugalforce and will be sleeve 22', these parts being held against accidentalseparation by any suitable means such as a set screw or set screws 23.The numeral 26' designates variable pitch blades which are of r Theheads are provided with openings 21,

to receive stabilizing arms 23. These arms have their inner endsthreaded into the openings 21 and the parts are held against accidentaldis- The stabilizing arms 28 extend outwardly beyond the hub l0 and passthrough the openings between the rings l2 and are-radial when the bladesare at the desired minimum pitch. These stabilizing arms swing in adirection longitudinally of the axis of rotation of the hub. Thestabilizing arms are provided at their ends with heads 30, suitablyscrewed thereto.

Disposed preferably upon the front of the ropeller is a pressureop'erated element or disc 3|, which is preferably circular and stifl.This pressure element or disc is of airfoil formation and has agenerally concave front surface and a rear cambered surface, as shown at32, produced by an inclined or transversely curved marginal portion 33..The element'or disc 33 is provided centrally thereof with a largeopening 33, having a considerably larger diameter than the shaft l4.Upon the front side ofthe element or disc 30 is annular flange 35,spaced from the opening and surrounding the same, and receiving andholding a flexible or resilient coupling 36, preferably formed ofrubber. This coupling has an opening 31, to receive the reduced end of asleeve 38 and a ring 39, posi-. tioned at the rear of the coupling 36,andclamped to the sleeve 38. The sleeve 33 is slidably mounted upon theshaft ll. Since the element or .disc 3| is acted upon by centrifugalforce when the propeller is driven it will remain concentric with theshaft I l and very little strain By virtue of the shape in cross sectionof the element or disc 3| the air'pressure acting upon the front face ofthis element or disc during the travel of the vehicle is increased,whilea suction is created upon the rear face of the element or disc 3|by virtue of the camber 32 and the suction action created by thecentrifugal force of the blades drawing the air away from the element3|. The element 3| will therefore be,pushed rearwardly from its frontside and pulled rearwardly from its rear side.

The numeral 40 designates a pair of connecting arms, disposed at therear of the element or disc 3| and secured thereto, at ll. Theseconnecting arms extend generally longitudinally swung outwardly bycentrifugal force, asind icated by the dotted lines. At their rear endsthese connecting arms 40 have elongated slots 42, receiving the outerends of the -stabilizlng arms 28. Rollers 43 are disposed in the slots"and are mounted upon the connecting arms and these rollers are disposedat the front of the stabilizing arms 23 and engaged therewith. It isthus apparent that when the pressure elem nt or disc 3| moves rearwardlywith respect to the shaft ,thi movement will be transmitted to thestabilizing arms 28,- through the me- .dium of the connecting arms 40,whereby the" stabilizing arms 28 will assume rearwardly inclinedpositions. This rearwardly inclined position of the stabilizing arms 28is shown in Figure 4, and the inclination of the stabilizing arms willcause the roll'ers43 to travel more readily toward the outer ends of thestabilizing arms,.

and this action is also aided by the free ends of the connecting arms 40moving outwardly by centrifugal force. The heads 30 prevent theconnecting arms from separating from the stabilizing arms as.

The operation of the propeller is as follows:-

, wide open and the propeller will be driven at the maximum speed whichmay be 2000 R. P. M. When the aircraft is placed in flight it iscustomary to reduce the speed of the engine considerably below themaximum speed. This is 1 ,done by the operator and automatically reducesthe torque. When my propeller is used, the blades being at the desiredminimum pitch before the flight is started, the propeller may be drivenat the maximum speed. When the aircraft is placed into flight, thetravel of'the aircraft causes the air currents to exert a rearwardpressure upon thefront face of the pressure operated element or'disc 3|and a suction upon the rear face, with the result that the element 3| isshifted rearwardly upon the' shaft I4 and the stabilizing arms 23 areswung rearwardly and the blades 24 are turned upon their. longitudinalaxis to increase the pitch of the blades. When this occurs the speed ofthe engine will be automatically slowed down but it will be found thatthe torque of the motor while rotating at the reduced'speed will remainsubstantially constant to the torque when rotating at the higher speed.This takes place with the throttle remaining unchanged.

Since the element or disc 3| has a universal mounting upon the shaft I4,it will permit of a differential pitch action between the propellerblade for having a smooth operation. This differential of pitchadjustment is effected by the air pressure upon the blades and underthese conditions the element or disc 3| and associated ele-- mentspermit of this differential action.

In Figure 7 I have shown a modified form of the invention. In this formof the invention the element or disc 3| and connecting arms 40 v areomitted and pressure. operated elements 44 and extend longitudinally ofthe blades and preferably terminate at the outer ends of the sleeves 22.Each element 44 has an airfoil formation with an outer cambered surface,as shown at 45 and an inner preferably flat surface 46. These elements44 are tilted upon their longitudinal axes so that they convergerearwardly. All other parts of the propeller remain the same asdescribed in connection with the first form of the invention.

The operation of this form of the propeller is as follows: When thepropeller'is being driven before the aircraft is in flight, thestabilizing arms 28 are in the radial position and the blades 24 assumethe desired minimum pitch. When the aircraft is in flight, the rearwardaction of the air pressure acting upon the pressure elements 44 shiftthem rearwardly turning the stabilizing arms rearwardly and increasingthe pitch of the blades of the propellers. This will slow down h pitchof the blades, a pressure operated element movable longitudinally of thehub, and connecting arms secured to the element and engaging the outerportions of the arms and shifted laterally toward the outer ends of thearms by the inclination of the arms.

2. A propeller comprising a hub, blades mounted,upon the hub and movablewith relation thereto to vary their pitch, generally radial armsconnected with the blades, a pressure operated element arranged near thehub, and centrifugally operated elements connected with the pressuremovable toward the outer ends of the arms.

3. A propeller comprising a hub, blades mounted upon the hub and movablewith relation to the hub to vary their pitch, generally radial armsconnected with the blades, a pressure element arranged near the hub, andresilient connecting arms secured toithe hub and connected with thegenerallyradial arms.

4. A propeller comprising a hub, blades mounted uponthe hub and movablewith relation "thereto to vary their pitch, a shaft connected with thehub and extending axially of the same, a sleeve mounted upon the shaftto move longitudinally thereof, an air pressure element, a universalmounting connecting the air pressure element with the sleeve, and meansconnecting the element with the blades, th air pressure element beingengaged by the air pressure caused by the travel of the aircraft or thelike and shifted thereby rearwardly upon the shaft.

5. A propeller for aircraft or the like, comprising ahub, a shaftattached to the forward end of the hub and extending axially thereof,generally radial blades having shanks pivotally mounted upon the hub sothat the shanks and blades turn upon their longitudinal axes to vary thepitch of the blades, generally radial arms attached to the shanks andswinging axially of the hub, an air pressure element arranged in.advance of the hub to engage with air pressure caused by the travel ofthe aircraft and to be shifted thereby rearwardly and axially of thehub, a universal mounting attached to the air pressure element andslidable upon said shaft,

and arms attached to the air pressure element and engaging the generallyradial arms, the generally radial arms being acted upon b centrifugalforce to turn the blades to reduce their pitch. WALTER W. EVERTS.

